An inherited form of early-onset diabetes mellitus has been discovered in a line of Keeshond dogs. Sixty percent of all dogs in three litters with a common sire, developed clinical signs of diabetes mellitus from two to four months of age. These signs included polyuria, polydypsia, glycoseuria, intolerance to glucose loading, hypoinsulinemia, hyperglycemia, hypercholesterolemia, hypertriglyceridemia, and bilateral catracts. We propose to establish a breeding colony to perpetuate this genetically determined disease so that it can be characterized further in terms of its genetic, morphologic, and biochemical characteristics. The ultimate goal is to provide a suitable animal model of early-onset diabetes mellitus that will be useful in solving important problems relating to diabetes mellitus and its complications in man. Canine diabetes will be characterized by clinical, opthalmic, radiographic, biopsy, necropsy, and biochemical techniques. Plasma glucose, insulin, cortisone, thyroxin, glucagon, cholesterol, triglycerides, phospholipid, and free fatty acid concentrations will be determined. Tissues will be subjected to both light and electron microscopy. Affected dogs will be made available to other investigators when sufficient numbers are on hand.